000
FXUS62 KRAH 091448
AFDRAH
Area Forecast Discussion
National Weather Service Raleigh NC
950 AM EST Fri Dec 9 2016
.SYNOPSIS...
Arctic high pressure will build across the area through Saturday. A
cold front will approach from the west late Sunday and move through
the area on Monday.
&&
.NEAR TERM /THROUGH TONIGHT/...
As of 950 AM Friday...
Forecast is in good shape. A large area of arctic high pressure
continues to build in from the NW today, with fast mid level flow
from the WNW and a dry column. A weak wave passing by to our north
is responsible for the sporadic snow showers on the western slopes,
but neither these nor the associated cloud cover will survive
crossing the mountains. The observed thickness at GSO this morning
was 1278 m, well below the seasonal normal, and steady cold air
advection today will not afford much of a rise, even with ample
sunshine. Temps so far this morning are running a degree or so above
the forecast pace, so have nudged up temps accordingly this
afternoon by a degree or so, peaking at 40-46. -GIH
The expansive arctic high pressure currently centered over nation`s
mid-section will build slowly eastward into the area through the
weekend. Aloft, trailing channeled shortwave energy, associated with
the closed low moving out over the Canadian Maritimes will traverse
the Mid-Atlantic region today. However, it will prove of little
consequence as the cP airmass in place(PWATS ~ 0.10") is just too
dry to support any clouds.
With H8 temps -10 Celsius(2 to 3 standard deviations below normal)
and low-level thicknesses bottoming around 1275 meters(45 meters
below normal), temperatures will will run a good 10 to 15 degrees
below normal. Highs in the upper 30s to lower 40s. Lows in upper
teens to lower 20s.
&&
.SHORT TERM /SATURDAY AND SATURDAY NIGHT/...
As of 200 AM Friday...
Flow aloft transitions to zonal on Saturday. Otherwise, very little
little change as the modified arctic high pressure migrates east
atop the region. Temperatures Saturday and Saturday night will be
very similar to today and tonight. Highs 40 to 45.
Lows 20 to 25.
&&
.LONG TERM /SUNDAY THROUGH THURSDAY/...
As of 400 AM Friday...
Overview: Long range model guidance has come into better agreement
on Sunday/Monday, however, considerable uncertainty plagues the
remainder of the extended forecast.
Sun/Mon: A shortwave trough and attendant low pressure system
expected to move onshore the Pacific NW on Saturday is progged to
track rapidly east across the Upper Midwest (Sun), Great Lakes (Sun
night), and New England (Mon) via a 125-150 knot upper level jet
extending from coast-to-coast at ~40 degrees latitude. An associated
cold front will rapidly approach the mountains from the west Sunday
night, however, the front will slow down as it tracks SE through the
Carolinas on Monday and will likely stall in a west-east orientation
over the Deep South/Southeast Tuesday morning. With the above in
mind, expect increasing cloud cover and highs in the 40s on Sunday
(coolest NW/warmest SE), with light rain assoc/w southerly return
flow /warm advection/ possible Sunday evening/night, primarily in
the SE coastal plain. Chances for precipitation will increase on
Monday as the front progresses into the Carolinas. Temperatures on
Monday will be a function of strong warm advection, cloud cover, and
precipitation, resulting in low confidence. At this time will
indicate highs ranging from the mid 50s NW to mid/upper 60s SE.
Mon Night-Thu: Considerable uncertainty persists from Monday night
onward as the aforementioned front stalls in a west-east orientation
across the Deep South/Southeast, beneath an energetic upper level
pattern characterized by numerous small amplitude waves embedded
within a ~150 knot jet that extends from the Pacific to the
Atlantic. With confidence so low, will make little change to this
period of the forecast. -Vincent
&&
.AVIATION /12Z FRIDAY THROUGH TUESDAY/...
As of 620 AM FRIDAY...
24-Hour TAF period: Very Dry air associated with the cP airmass
building into the area will support VFR conditions through the TAF
period. Winds will be northwesterly, generally 5-10 mph this
morning will increase to around 10 mph with gusts of 15-20 mph in the
afternoon.
Looking ahead: VFR conditions are expected through the weekend.
There is a small chance of sub-VFR ceilings on Sunday, with better
chances Monday and Tuesday.
&&
.RAH WATCHES/WARNINGS/ADVISORIES...
None.
&&
$$
SYNOPSIS...CBL
NEAR TERM...Hartfield/CBL
SHORT TERM...CBL
LONG TERM...Vincent
AVIATION...CBL